Example plot in Manual lacks text

[Michael D. Godfrey]

>
> How can we determine if "convert.exe" exists for Windows?
It is likely that Windows has a "which" command.  We need a windows
expert...

In any case, it would be good to remove "pdf" from the terminal list
for gnuplot 4.2.3  (in fact for all 4.2 versions) since now the use of "pdf"
just crashes.

Is ghostscript required for windows, or is there some other way to
generate the manual?  If ghostscript is required and it is not possible to
test for convert, then I would say just use gs instead of convert.  I tested
both and they both work.

I am copying John on this in case he has a definite preference.
For jwe:  the background is:  currently Octave fails on print("xxx.pdf")
for systems running gnuplot 4.2.xx.  The reason for this is that the 4.2
gnuplots do not have a terminal type pdf.  The 4.2 Manual says that pdf
is supported, but it is not true.  (Also, the gnuplot web page lists 
support for
pdf as a new feature in 4.3.)  Currently, the print command has code that
runs "convert" in cases such that gnuplot does not have the terminal type,
but convert can make the conversion from a type supported by gnuplot.
Neither Ben nor I know if this code works on Windows systems, which may
not have "convert."  I ran a test replacing the "convert" call with 
"gs."  This
also works.  So, I have recommended:

1. Remove the pdf type as a type supported by gnuplot 4.2.xx.  This
    fixes the error when using print("xxx.pdf") in systems that have 
"convert."
    The current code assumes that "convert" exists in any case.

2. Consider switching from "convert" to "gs."  This is known to work for
    the pdf case in systems that have "gs" (Ghostscript).  This must be most
    supported systems since the install process assumes Ghostscript.  
(Used for
    the Figures in the Manual.  And, it would be nice to have the 
Figures in the
    Manual generated the same way that the example code would run for users.
    Until you made the recent change from png to pdf, the code in the Manual
    did not produce the Figure shown in the Manual.)   However, this change
    would need to be tested for all cases that end up calling the convert
    code.

Do you have a preference about this?